Thirty nine volunteers attended a program at the Elk River City Hall Tuesday morning to learn basic techniques for uncovering the presence of emerald ash borer larvae, in particular increased woodpecker activity in ash trees in the early spring.
Sherburne Soil and Water District (SWCD) Conservationists Gina Hugo and Bill Bronder were joined by Jennifer Dippel and Angie Ambourn, plant health specialists from the MN Dept. of Agriculture, who conducted a presentation using the Minnesota Forest Pest First Detector Manual, a publication which includes tips for identifying the black, green and white ash varieties found in Minnesota, which are sometimes mistaken for box elder, black walnut, butternut and hickory trees. Mature ash trees usually have a deeply furrowed gray bark with a diamond or honeycomb pattern, and the leaves of the black and green ash turn yellow in the fall, with the white ash leaves turning a maroon color.
The EAB infestation has reached Hennepin and Ramsey counties, Dippel said, and EAB has been confirmed as far north as Superior, WI, though no confirmed cases have yet been reported in the Duluth area. While the adult insect can fly up to five miles, it usually expands its range slowly, with a half-mile increase per year being common. Infestation seen on maps appears to follow major highways, which would indicate that untreated firewood transportation plays a major role in the spread of the problem.
Cases of EAB have been confirmed as far west as Colorado, while metropolitan areas in Pennsylvania, Ohio, Indiana, Illinois, Michigan and Iowa have all been afflicted in recent years. The Detroit area has been especially hard-hit, with long boulevards of ash trees now simply rows of stumps.
In Minnesota, EAB has been confirmed in Hennepin, Ramsey, Olmsted, Winona and Houston counties to date, and it is expected that the insects will be moving into Anoka County in the near future.
Firewood that has not been kiln-treated cannot be transported from a “Quarantine County,” Ambourn said, unless the adjoining destination county is also under quarantine. Gas station and convenience store firewood must be labeled as having been treated prior to sale, but enforcement of regulations regarding private sales or use is extremely difficult.
Treatment and Prevention
EAB is a destructive wood-boring insect native to the Far East and eastern Russia. It normally has a one-year life cycle, overwintering as full-grown larvae in chambers created under the bark of ash trees. The larvae feed, creating tell-tale “S”-shaped tunnels in the bark and outer sapwood that “girdle” the trees, interrupting the flow of water and nutrients. Adult EAB emerge through distinctive “D”-shaped exit holes and feed on the ash leaves before mating and laying eggs on the tree bark to restart the destructive cycle.
The current survey will take place between March 13 and April 17, the early spring time when woodpeckers will be most active in detecting and drilling into the bark to extract and eat the EAB larvae. Survey volunteers will use binoculars to study upper ash tree surfaces for evidence of woodpecker activity and “blonding,” a change in bark color also indicative of EAB activity.
The manual states chemical treatment of ash trees should not be carried out if there has been no infestation within a 15-mile radius. Hugo maintains a file of qualified arborists at her SWCD office who are trained to treat ash trees in the event of an EAB infestation being discovered locally, she said. More on insecticide options at www.emeraldashborer.info or www.extension.umn.edu/issues/eab.
Other treatments being considered include importation of the “smokey-winged beetle bandit,” a stingless wasp whose larvae prey on EAB larvae, as well as other insect predator species.
Surveys will take place on maintained trees in parks, at compost sites and on private property for which permission has been granted. Hugo has created and will maintain data sheets for each survey group, which will also create maps of surveyed areas using the GPS units in their smart phones.
Learning to distinguish adult EAB can also be a challenge, according to the presentation, with a number of other insect types often mistaken for it, such as the dogbane beetle, sixspotted tiger beetle, blister beetle, green stink bug, bronze birch borer and the flatheaded apple tree borer.
The presentation also touched on the Asian long-horned beetle, which is currently attacking hardwoods along the east coast of the U.S., and the sirex woodwasp, which attacks healthy pines and has been found in the eastern U.S. and Canada.
For more information or to report a suspected sighting of invasive insect pests, contact the Mn Dept. of Agriculture’s “Arrest the Pest hotline” at Arrest.The.Pest@state.mmn.us, or call 888-545-6684 to report suspicious insects.
Following the indoor portion of the program, the volunteers and presenters went outdoors to view some local ash trees and to discuss what to look for when surveying area examples. Woodpecker holes will be small and not very deep, Dippel said, so binoculars will be essential in finding then on a tree suspected of an EAB infestation.